The field of the disclosure relates generally to airfoils and more particularly to airfoils including a body portion and a tip portion coupled to the body portion.
At least some known airfoils include a tip portion and a body portion. Under at least some operating conditions, the tip portion and the body portion experience different loads. In at least some known airfoils, the tip portion and the body portion are assembled separately and are configured to withstand different loads and different temperatures. While the tip portion is typically configured stronger than the blade portion, after a period of time in service, the tip portion may become eroded, oxidized, and/or corroded by impingement of the hot combustion gases, or the like. Because the airfoil may be expensive to produce, repair or refurbishment of the damaged airfoil may be preferred if possible. In at least some known airfoils, the body portion of the airfoil is formed in an open-tip or tipless casting process and the tip portion is coupled to the body portion after the body portion is formed. The use of open tip or tipless turbine blade casting allows improved casting yield by reducing core shift during single-crystal directional solidification process. Reducing core shift is critical in producing high cooling efficient thin-walled turbine blades. However, subsequent to casting the body portion, one has to bond or build a blade tip on top of the tipless body portion.
Similarly, during the repair of an airfoil, the damaged tip portion may be removed, such as through grinding, to allow for a replacement tip portion to be welded or otherwise attached to the body portion. However, in both initial manufacture of the airfoil, or in repair of the airfoil, coupling the tip portion to the body portion requires that the tip portion be precisely aligned on the body portion, as well as any features, such as one or more interior cooling passages extending through the body portion and the tip portion. The meticulous procedure needed to align the parts is laborious, tedious and production non-friendly. For at least some known airfoils, the alignment process requires specialized equipment. For example, to assemble at least some known airfoils, the tip portion is positioned on the body portion and clamped in position. In many instances, the common cast tip can have issues with alignment of the cooling passages to an unfamiliar blade. If the tip portion and the body portion are misaligned, the airfoil has an increased risk of failure during its service life.